package restic

import (
	"context"
	"iter"

	"github.com/restic/restic/internal/backend"
	"github.com/restic/restic/internal/crypto"
	"github.com/restic/restic/internal/errors"
	"github.com/restic/restic/internal/ui/progress"
)

// ErrInvalidData is used to report that a file is corrupted
var ErrInvalidData = errors.New("invalid data returned")

// Repository stores data in a backend. It provides high-level functions and
// transparently encrypts/decrypts data.
type Repository interface {
	// Connections returns the maximum number of concurrent backend operations
	Connections() uint
	Config() Config
	PackSize() uint
	Key() *crypto.Key

	LoadIndex(ctx context.Context, p TerminalCounterFactory) error

	LookupBlob(t BlobType, id ID) []PackedBlob
	LookupBlobSize(t BlobType, id ID) (size uint, exists bool)

	NewAssociatedBlobSet() AssociatedBlobSet
	// ListBlobs runs fn on all blobs known to the index. When the context is cancelled,
	// the index iteration returns immediately with ctx.Err(). This blocks any modification of the index.
	ListBlobs(ctx context.Context, fn func(PackedBlob)) error
	ListPacksFromIndex(ctx context.Context, packs IDSet) <-chan PackBlobs
	// ListPack returns the list of blobs saved in the pack id and the length of
	// the pack header.
	ListPack(ctx context.Context, id ID, packSize int64) (entries []Blob, hdrSize uint32, err error)

	LoadBlob(ctx context.Context, t BlobType, id ID, buf []byte) ([]byte, error)
	LoadBlobsFromPack(ctx context.Context, packID ID, blobs []Blob, handleBlobFn func(blob BlobHandle, buf []byte, err error) error) error

	// WithUploader starts the necessary workers to upload new blobs. Once the callback returns,
	// the workers are stopped and the index is written to the repository. The callback must use
	// the passed context and must not keep references to any of its parameters after returning.
	WithBlobUploader(ctx context.Context, fn func(ctx context.Context, uploader BlobSaverWithAsync) error) error

	// List calls the function fn for each file of type t in the repository.
	// When an error is returned by fn, processing stops and List() returns the
	// error.
	//
	// The function fn is called in the same Goroutine List() was called from.
	List(ctx context.Context, t FileType, fn func(ID, int64) error) error
	// LoadRaw reads all data stored in the backend for the file with id and filetype t.
	// If the backend returns data that does not match the id, then the buffer is returned
	// along with an error that is a restic.ErrInvalidData error.
	LoadRaw(ctx context.Context, t FileType, id ID) (data []byte, err error)
	// LoadUnpacked loads and decrypts the file with the given type and ID.
	LoadUnpacked(ctx context.Context, t FileType, id ID) (data []byte, err error)
	// SaveUnpacked stores a file in the repository. This is restricted to snapshots.
	SaveUnpacked(ctx context.Context, t WriteableFileType, buf []byte) (ID, error)
	// RemoveUnpacked removes a file from the repository. This is restricted to snapshots.
	RemoveUnpacked(ctx context.Context, t WriteableFileType, id ID) error

	// StartWarmup creates a new warmup job, requesting the backend to warmup the specified packs.
	StartWarmup(ctx context.Context, packs IDSet) (WarmupJob, error)
}

type FileType = backend.FileType

// These are the different data types a backend can store. Only filetypes contained
// in the `WriteableFileType` subset can be modified via the Repository interface.
// All other filetypes are considered internal datastructures of the Repository.
const (
	PackFile     = backend.PackFile
	KeyFile      = backend.KeyFile
	LockFile     = backend.LockFile
	SnapshotFile = backend.SnapshotFile
	IndexFile    = backend.IndexFile
	ConfigFile   = backend.ConfigFile
)

// WriteableFileType defines the different data types that can be modified via SaveUnpacked or RemoveUnpacked.
type WriteableFileType backend.FileType

const (
	// WriteableSnapshotFile is the WriteableFileType for snapshots.
	WriteableSnapshotFile = WriteableFileType(SnapshotFile)
)

func (w *WriteableFileType) ToFileType() FileType {
	switch *w {
	case WriteableSnapshotFile:
		return SnapshotFile
	default:
		panic("invalid WriteableFileType")
	}
}

type FileTypes interface {
	FileType | WriteableFileType
}

// LoaderUnpacked allows loading a blob not stored in a pack file
type LoaderUnpacked interface {
	// Connections returns the maximum number of concurrent backend operations
	Connections() uint
	LoadUnpacked(ctx context.Context, t FileType, id ID) (data []byte, err error)
}

// SaverUnpacked allows saving a blob not stored in a pack file
type SaverUnpacked[FT FileTypes] interface {
	// Connections returns the maximum number of concurrent backend operations
	Connections() uint
	SaveUnpacked(ctx context.Context, t FT, buf []byte) (ID, error)
}

// RemoverUnpacked allows removing an unpacked blob
type RemoverUnpacked[FT FileTypes] interface {
	// Connections returns the maximum number of concurrent backend operations
	Connections() uint
	RemoveUnpacked(ctx context.Context, t FT, id ID) error
}

type SaverRemoverUnpacked[FT FileTypes] interface {
	SaverUnpacked[FT]
	RemoverUnpacked[FT]
}

type PackBlobs struct {
	PackID ID
	Blobs  []Blob
}

type TerminalCounterFactory interface {
	// NewCounterTerminalOnly returns a new progress counter that is only shown if stdout points to a
	// terminal. It is not shown if --quiet or --json is specified.
	NewCounterTerminalOnly(description string) *progress.Counter
}

// Lister allows listing files in a backend.
type Lister interface {
	List(ctx context.Context, t FileType, fn func(ID, int64) error) error
}

type ListerLoaderUnpacked interface {
	Lister
	LoaderUnpacked
}

type Unpacked[FT FileTypes] interface {
	ListerLoaderUnpacked
	SaverUnpacked[FT]
	RemoverUnpacked[FT]
}

type ListBlobser interface {
	ListBlobs(ctx context.Context, fn func(PackedBlob)) error
}

type BlobLoader interface {
	LoadBlob(context.Context, BlobType, ID, []byte) ([]byte, error)
}

type WithBlobUploader interface {
	WithBlobUploader(ctx context.Context, fn func(ctx context.Context, uploader BlobSaverWithAsync) error) error
}

type BlobSaverWithAsync interface {
	BlobSaver
	BlobSaverAsync
}

type BlobSaver interface {
	// SaveBlob saves a blob to the repository. ctx must be derived from the context created by WithBlobUploader.
	SaveBlob(ctx context.Context, tpe BlobType, buf []byte, id ID, storeDuplicate bool) (newID ID, known bool, sizeInRepo int, err error)
}

type BlobSaverAsync interface {
	// SaveBlobAsync saves a blob to the repository. ctx must be derived from the context created by WithBlobUploader.
	// The callback is called asynchronously from a different goroutine.
	SaveBlobAsync(ctx context.Context, tpe BlobType, buf []byte, id ID, storeDuplicate bool, cb func(newID ID, known bool, sizeInRepo int, err error))
}

// Loader loads a blob from a repository.
type Loader interface {
	LoadBlob(context.Context, BlobType, ID, []byte) ([]byte, error)
	LookupBlobSize(tpe BlobType, id ID) (uint, bool)
	Connections() uint
}

type WarmupJob interface {
	// HandleCount returns the number of handles that are currently warming up.
	HandleCount() int
	// Wait waits for all handles to be warm.
	Wait(ctx context.Context) error
}

// FindBlobSet is a set of blob handles used by prune.
type FindBlobSet interface {
	Has(bh BlobHandle) bool
	Insert(bh BlobHandle)
}

type AssociatedBlobSet interface {
	Has(bh BlobHandle) bool
	Insert(bh BlobHandle)
	Delete(bh BlobHandle)
	Len() int
	Keys() iter.Seq[BlobHandle]
	Intersect(other AssociatedBlobSet) AssociatedBlobSet
	Sub(other AssociatedBlobSet) AssociatedBlobSet
}
